Migrate `pallet-assets-freezer` to umbrella crate (#6599)
Part of https://github.com/paritytech/polkadot-sdk/issues/6504
### Added modules
- `utility`: Traits not tied to any direct operation in the runtime.
polkadot address: 14SRqZTC1d8rfxL8W1tBTnfUBPU23ACFVPzp61FyGf4ftUFg
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Co-authored-by:
Giuseppe Re <giuseppe.re@parity.io>
parent
569ce71e